1. Field of the Invention
The present invention relates to a video signal processing apparatus for increasing a frame display frequency of an input video signal.
2. Description of the Related Art
Some display devices, such as television receivers, employ a double-speed driving method for increasing a frame display frequency (frame rate) to suppress flicker and blurring of motion. As the double-speed driving method, an intermediate image generating method for generating an intermediate corrected image by motion detection and a spatial frequency separating method for separating an image corresponding to an input video signal into a low-frequency component image and a high-frequency component image in a spatial frequency domain and displaying the low-frequency component image and the high-frequency component image are known.
The intermediate image generating method is for detecting motion of an object in an input video signal, and estimating and generating an image between two frames. Japanese Patent Laid-Open No. 2004-159294 discloses a method for generating an interpolation frame from a first reference frame and a second reference frame that follows the first reference frame.
In the spatial frequency separating method, filtering is executed on each frame of an input video signal to separate the input video signal into a spatial high-frequency component and a spatial low-frequency component. For example, the spatial high-frequency component is then collected in one sub-frame, whereas the spatial low-frequency component is distributed to both sub-frames. Sub-frames are frames displayed in the double-speed driving method. A plurality of sub-frames corresponds to one frame of the input video signal depending on a frame display frequency. Japanese Patent Laid-Open No. 2006-184896 discloses a method for reducing a high-frequency component of at least one sub-frame when one frame is divided into a plurality of sub-frames in accordance with an increase in a frame display frequency.
However, image quality may decrease by increasing the frame display frequency (frame rate) depending on video to be displayed.
More specifically, for example, if motion is incorrectly detected in the intermediate image generating method, an incorrect intermediate image is generated, which may result in image quality degradation.
In addition, for example, if neighboring pixels of an image of an input video signal has a large luminance value difference in the spatial frequency separating method, a contour or the like may remain in a low-frequency component image thereof. In such a case, jaggy is caused in reproduced images and image quality may decrease.